Shield for radio receiver dial lamps



Nov. 15, 1949 SHEA 2,488,244

SHIELD FOR RADIO RECEIVER DIAL LAMPS Filed May 14. 1949 BY Ming 5 Patented Nov. 15, 1949 SHIELD FOR RADIO RECEIVER DIAL LAMPS Frank Michael Shea, Cincinnati, Ohio, assignor to Avco Manufacturing Corporation, Cincinnati, Ohio, a corporation of Delaware Application May 14, 1949, Serial No. 93,353

2 Claims. 1

The present invention relates to devices for shielding electrostatic flux, and specifically to a novel shield employed to minimize noise interference in radio or television receivers of the type caused by the dial lamp.

The object of the invention is to provide an electrostatic shield in the form of a coil comprising a few spirally-wound turns of conductive material, of such character that it may be cheaply manufactured in mass quantities and easily and quickly assembled.

For a better understanding of the present invention, together with other and further objects and advantages thereof, reference is made to the following detailed description of the accompanying drawings, in which there is shown an illustrative preferred form of R. F. shield in accordance with the invention.

Fig. 1 is a perspective view, taken from the side, of a shield in accordance with the invention and a socket assembly to which the shield is engaged, this socket assembly being adapted to receive a bulb for illuminating the dial of a radio receiver;

Fig. 2 is another perspective View, also taken from the side, of the novel R. F. shield and the socket assembly illustrated in Fig. 1, with the bulb in place, the socket assembly having been axially rotated through 90 from the position illustrated in Fig. 1; and

Fig. 3 is a perspective view of a radio receiver with dashed lines on the right side thereof indicating the disposition of the novel R. F. shield in accordance with the invention and the socket assembly.

In Fig. 3 of the drawings there is shown a radio receiver cabinet I having a conventional loud speaker grille l2, a tuning dial it, and controls l4, l5, and It. This cabinet contains a chassis ll, one end of which is indicated in dashed outline. Secured to this chassis, as by a bolt and nut I8, is a mounting bracket ll which has a vertically extending main portion, an intermediate integral horizontal portion, and a vertically extending top portion. Mounted on this top portion is a terminal l9 apertured as indicated at 2| and 22 (Fig. 1) to receive rivets 2i] and 23 which secure the terminal in place. The members ll, Ill, and I9 will be understood to be at R. F. ground potential. Terminal I9 has a generally L-shaped configuration. It is apertured to receive another terminal is, insulated as by a washer member 23 and other provisions from terminal [9. Mounted on portion 21 of terminal I9 is a socket 26, the

nected as by contact with terminal 21. The inner or base terminal of the socket is brought out to terminal It will be understood that terminal is is R. F. grounded, and that terminal 29 is at a potential different from ground, which is a function of filament current and resistance.

Screwed into socket 26 is a dial lamp 24 having a base 25.

The elements so far specifically described are conventional in character and well-known to those working in this art. Those elements, comprising a conventional dial lamp, cause serious noise interference, particularly in A. C.D. C. receivers employing loop aerials. This noise is caused by vibration and considered by authorities to emanate from the function of the filament coil with the wire which supports it, internally of bulb 24. When the filament coil vibrates it moves relative to its anchor Wires, forming minute sparks which radiate radio frequency interference directly to the loop aerial, particularly when the loop is mounted inside the cabinet and in proximity to the dial lamp. Interposing a grounded metal shield between the lamp bulb and the loop aerial is an excellent expedient for eliminating this trouble.

In accordance with the invention there is provided a simple and commercially practical device for performing this function. This device comprises a spirally-wound coil 30 of conductive material. t is conventional for the screw threads of socket 26 to be so formed thereon that exterior threads appear on the outside of the socket. Coil 38 is so formed that approximately the first two turns thereof complement and interfit with the exterior threads on socket 26, so that the R. F. shield can be installed in place by simply being screwed onto the socket. The diameter of the convolutions increases as the coil progresses away from the socket and toward the lamp bulb. It is desirable to continue the convolutions outwardly to the region of the filament mounting. The inner end of coil 38 is in direct contact with socket 26 and is therefore R. F. grounded. It has been found in commercial practice that the presence or absence of this type of shield can be very easily observed by the ear, and that measuring and amplifying instruments are not necessary for the observation of the advantage of the invention in suppressing noise interference of the type mentioned above. Further, the cost of manufacture and installation of the shield is very, very small.

outer or shell terminal of which is directly con- While there has been shown and described 3 what is presently considered to be the preferred embodiment of the present invention, it will be understood by those skilled in the art that various modifications may be made therein Without departing from the true scope of the invention as defined by the appended claims.

I claim:

1. In a radio receiver of the type including a source of noise interference in the form of a dial lamp having a grounded socket formed with exterior threads thereon, an R. F. electrostatic fluxshielding device for suppressing such interference, comprising a coil of conductive material having at least one convolution so formed as to engage with such screw threads and other convolutions so formed as to surround the exterior of the bulb of said lamp.

2. In a radio receiver of the type including a REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,848,970 Thompson Aug. 10, 1920 2,358,491 Del Camp Sept. 19, 1944 

